This invention relates generally to internal combustion engines. More particularly the invention relates to control of EGR (exhaust gas recirculation) in a turbocharged diesel engine. The invention also relates to monitoring certain events involving emission control.
Controlled engine exhaust gas recirculation is a known technique for reducing oxides of nitrogen in products of combustion that are exhausted from an internal combustion engine to atmosphere. A typical EGR system comprises an EGR valve that is controlled in accordance with engine operating conditions to regulate the amount of engine exhaust gas that is recirculated to the intake flow entering the engine so as to limit the combustion temperature and hence reduce the formation of oxides of nitrogen during combustion. To the extent that exhaust gas is introduced into the flow entering the engine, it displaces air that would otherwise enter the engine.
Supercharging is one method for increasing engine torque and power. One type of supercharger comprises a turbocharger that comprises a compressor that boosts intake system pressure and a turbine that is powered by engine exhaust to operate the compressor. It is believed that turbocharged engines may provide fuel economy improvements for enabling vehicle manufacturers to achieve both mandated fuel economy requirements and a desired level of engine performance. However, because such engines must also comply with mandated tailpipe emission requirements, they are likely to require EGR systems.
A general aspect of the invention relates to a control system for a valve that controls exhaust gas recirculation in an internal combustion engine by selectively positioning a valve element that establishes the extent to which the valve is open. The control system comprises a processor that is configured for processing data in feedback control of the position of the valve element to develop from the data a position control signal for setting the extent to which the valve is open, including processing data corresponding to actual position of the valve element and data representing a desired position of the valve element to develop a position error signal, processing data that defines actual EGR rate and data representing a desired EGR rate to develop a rate error signal, and processing the position error signal and the rate error signal to develop the position control signal.
Another general aspect relates to a method for control of exhaust gas recirculation in an internal combustion engine by selectively positioning a valve element that establishes the extent to which an exhaust gas recirculation valve is open. The method comprises processing data in feedback control of the position of the valve element to develop from the data a position control signal for setting the extent to which the valve is open, including processing data corresponding to actual position of the valve element and data representing a desired position of the valve element to develop a position error signal, processing data that defines actual EGR rate and data representing a desired EGR rate to develop a rate error signal, and processing the position error signal and the rate error signal to develop the position control signal.
Still another aspect relates to an event monitoring system in an exhaust gas recirculation system of an internal combustion engine comprising an exhaust gas recirculation valve through which exhaust gas is recirculated and which comprises a valve element that is selectively positioned by a position error signal in a feedback loop of a closed loop control to establish the extent to which the valve is open. The event monitoring system comprises a valve monitor for monitoring the time for which the magnitude of the position error signal exceeds a position error threshold and for logging the occurrence of an event when the time for which the magnitude of the position error signal exceeds the position error threshold exceeds a time threshold.
Still another aspect relates to a method of event monitoring in an exhaust gas recirculation system of an internal combustion engine comprising an exhaust gas recirculation valve through which exhaust gas is recirculated and which comprises a valve element that is selectively positioned by a position error signal in a feedback loop of a closed loop control to establish the extent to which the valve is open. The method comprises monitoring the time for which the magnitude of the position error signal exceeds a position error threshold and logging the occurrence of an event when the time for which the magnitude of the position error signal exceeds the position error threshold exceeds a time threshold.
Still another aspect relates to an event monitoring system in an exhaust gas recirculation control system of an internal combustion engine wherein the event monitoring system comprises a first monitor for monitoring the time for which the magnitude of a signal used in the control system exceeds a first threshold and for logging the occurrence of a first event when the time for which the magnitude of the signal exceeds the first threshold exceeds a first time threshold, and a second monitor for monitoring the time for which the magnitude of the signal exceeds a second threshold and for logging the occurrence of a second event when the time for which the magnitude of the signal exceeds the second threshold exceeds a second time threshold.
Still another aspect relates to an event monitoring system in an internal combustion engine emission control system wherein the event monitoring system comprises a first monitor for monitoring the time for which the magnitude of a signal used in the emission control system exceeds a first threshold and for logging the occurrence of a first event when the time for which the magnitude of the signal exceeds the first threshold exceeds a first time threshold, and a second monitor for monitoring the time for which the magnitude of the signal exceeds a second threshold and for logging the occurrence of a second event when the time for which the magnitude of the signal exceeds the second threshold exceeds a second time threshold.
Still another aspect relates to an event monitoring method in an internal combustion engine emission control system wherein the method comprises monitoring the time for which the magnitude of a signal used in the emission control system exceeds a first threshold and logging the occurrence of a first event when the time for which the magnitude of the signal exceeds the first threshold exceeds a first time threshold, and monitoring the time for which the magnitude of the signal exceeds a second threshold and for logging the occurrence of a second event when the time for which the magnitude of the signal exceeds the second threshold exceeds a second time threshold.
The accompanying drawings, which are incorporated herein and constitute part of this specification, include one or more presently preferred embodiments of the invention, and together with a general description given above and a detailed description given below, serve to disclose principles of the invention in accordance with a best mode contemplated for carrying out the invention.